Control mechanism



-Feb.'20, 1968 R.J.c|NKuTfs ETAL 3,369,409

CONTROL MECHANISM Filed Feb. le, 1965 Y j@ f ff a -D 77nd United StatesPatent Office 3,369,409 Patented Feb. 20, 1968 This invention relates toconcentric shaft mechanism, and in particular to dual concentricshaftrneans for tuning and adjusting electrical apparatus such as radioreceivers and the like. The invention has special reference to controlarrangements in which one shaft is enclosed and journalled withinanother, for instance an inner tuning shaft within an outer soundcontrol shaft.

In conventional apparatus the rotation of the outer shaft often disturbsthe setting of the inner shaft, especially when the mechanism controlledby the inner shaft is a sensitive tuner which inherently imposes only alow torque load on its shaft. It is the main object of this invention toavoid such disturbance. A further object is to provide plural shaftapparatus which is simple, reliable, and easy to combine with associateddevices.

Toward these objectives the invention provides a concentric shaft systemwherein a rst shaft, connectable to a low-torque load such as a tuner,has a brake advantageously engaged at all times and the action of whichsubstantially increases the torque required to turn this shaft. Thisbrake action prevents rotation of the low-torque shaft by other elementsof the concentric shaft system and hence avoids the disturbance formerlycaused by the turning of such other elements. In a preferred embodimentof our invention a brake drum is rigidly and coaxially secured to aninner and tuner-operating shaft. A pair of stationary brake shoes, onediametrically opposite the other, bear permanently against peripheralareas of the drum Preferably the drum is also used as part of a couplingwhich connects the inner shaft with the tuner mechanism.

The invention will be understood more fully from the followingdescription of the preferred embodiment thereof, incorporated in a radiotuner. In the drawing FIGURE l is a fragmentary plan View of the tuner,showing the new plural shaft system; FIGURE 2 is a generally similarview of the shaft system by itself; and FIGURE 3 is an exploded view ofthe new plural shaft apparatus. FIG- URES 4 and 5 are, respectively,perspective views of the new tuning shaft and brake drum subassembly andof the brake shoe device cooperating therewith.

Referring first to FIGURE l: the tuner 1t) of a radio receiver is shownas having a knob 11 which drives an inner shaft in the new concentricshaft apparatus 12, said shaft driving a worm gear transmission 13 forthe control of a core carriage 14 to shift magnetic cores 15 in thetuner. The shifting of cores, caused by the turning of knob 11,determines tuned characteristics of radio receiver circuits, not shown,which may for instance supply audio signals to a loudspeaker, not shown,forming part of said receiver.

The structure includes additional control means coaxial with tuning knob11, for instance knob 16 for adjusting the volume of sound produced bythe loudspeaker. This adjustment is effected with the aid of certaindevices in the new shaft structure 12, as will be mentioned more fullyhereinafter. Volume control knob 16 is fast on an outer shaft 17,wherein an inner shaft 18 is concentrically enclosed. Said inner shafthas one end connected to worm gear transmission 13 of the tuningmechanism, as will be described presently, while having an opposite endconnected with an innermost shaft 19 which is rigid with tuning knob 11,as will be understood from FIGURES l to 3. The interconnection of shafts18, 19 can be releasable in order to facilitate removal of the knobs, asis Well understood in the art.

According to the invention as fully illustrated in FIG- URES l to 4, thenew concentric shaft mechanism comprises a brake drum 20 rigidly securedto inner shaft 18 at the end thereof opposite tuning knob 11. As shownin FIGURES l and 5, a plurality of brake shoes 21, 22 are provided,uniformly bearing against this drum and symmetrically distributed aboutthe same. Usually it is sui- I cient for purposes of our invention toprovide a pair of brake shoes, one opposite the other, as: is shown inthe drawing. Brake drum 20 as shown in FIGURE 4 also provides, as afurther and axially terminal portion thereof, a coupling element 30.This element, as shown in FIG- URE l, normally engages worm gear drive13 of the tuner for driving the same` The new brake shoes 21, 22, asbest shown in FIGURE 5, are mounted on a stationary bearing structure 23confined in a housing 23', while this housing, by a suitable extensionthereof, supports shaft mechanism 12 on a rigid bracket 24 of tuner 1t)(FIGURE l). Each brake shoe is constructed in form of a small, elasticclip, held on this bearing structure 23, and each brake shoe has a freeend arranged to bear against the side or peripheral surface of brakedrum 20. Preferably the elastic clips or shoes are made of spring bronzeor the like. In FIGURE 3 the clips are removed from support 23 They areshown as having mounting ends 25 embedded in a groove 26 which is formedin bearing unit 23 (FIGURE 5). This bearing unit, as well as brake drumZtl thereon, can comprise a body of synthetic plastic material. Brakedrum 20 is coaxially riveted to inner shaft 18, see rivet element 27 inFIGURE 3.

The operation of the new apparatus is believed to be fairly obvious fromthe foregoing description of the structure. The user turns tuning knob11, thereby rotating inner shaft 18 and brake drum 20 thereon (FIGURE4). This drum, through coupling element 3G, rotates worm geartransmission 13, which in turn shifts core carriage 14 and adjusts tuner10 (FIGURE l). By virtue of the new construction the adjustment of thetuner remains undisturbed once the proper tuning has been achieved. Inparticular this adjustment is not disturbed, as it formerly often was,by operation of volume adjusting knob 16 and outer shaft 17 thereon.

This latter shaft is shown (FIGURE 3) having a top end 17, normallysecured to a conventional, rotatable potentiometer element 28 withinhousing 23', the potentiometer also having a stationary element 29secured to stationary support 23. The stationary element 29 normally isin contact with rotor 28, and is connected with tuner 10 by suitablecircuit means, not shown.

Heretofore trouble was often encountered with a tuner and the like whenan outer shaft was rotated to adjust a potentiometer or the like. As oneof these shafts was concentrically inserted in, and in surface contactwith the other (as also shown in FIGURE 2), and was not held to anyparticular angular orientation, the rotation of the outer shaft tendedto cause angular creeping or rotation of the inner shaft and thereby todisturb the delicate setting of the tuner. The trouble was particularlypronounced when a high gear ratio was: provided in the gear mechanism,as is desirable for precise tuning.

The invention overcomes the trouble by the use of brake drum 20 on theshaft of tuning knob 11, FIGURE 4, in conjunction with brake shoes 21,22 on bearing unit 23, FIGURE 5. The braking effect of these elementseffectively overcomes the creeping tendency of the inner shaft and theconsequent detuning effects. The new unit thus avoids the disturbanceheretofore caused by interaction of outer and inner shaft surfaces. Itavoids the kind of disturbance even if the torque load provided by tunerand its gear drive 13 is very small. The improvement is achieved by thetorque load which the brake imposes on tuning shaft I8.

As indicated in FIGURES 1, 4 and 5, the entire control apparatus,comprising brake unit Ztl, 21, 22 and bearing unit 23 for the same, isonly about as large as a pair of control knobs Il, 16. It can be evensmaller, The bearing unit, additionally containing potentiometerelements Z8, 29 therein, is conveniently mounted on tuner bracket l by arigid sleeve portion 31 extending from and coaxially to housing 23. Athreaded end 32 of the sleeve extends through a suitable aperture inbracket 24, and is fastened to this bracket by nut 33.

It will further be seen that internal surface 34, FIG- URE 3, is formedcoaxially within the rigid sleeve for rotation of external surface 3S ofouter shaft I7 therein, and that inner surface 36 of this shaft has arelatively wide front portion, separated from a relatively narrow rearportion by coaxial step 37. This step is engaged by a corresponding step3S in outside surface 29 of inner shaft I8. All of these and the matingsurface of inner shaft 18 are made as smooth as possible, and withsuitable sliding t. As will be clear from FIGURE 2, the inner shaft andbrake unit is prevented from forward displacement (downward in thedrawing) by the engagement of brake drum 20 with bearing unit 23, and isprevented from opposite or rearward displacement by bearing means 23 andby engagement between steps 37, 3S. In similar way, outer shaft 17 isprevented from forward and rearward displacement by wall 4t) of bearingunit 23 and potentiometer element 27, respectively.

It is preferred that the pressures applied by brake shoes 2l, 22 tobrake drum 2t) be purely radial and symmetrical. No forces are tnenencountered-for instance at step 37, 38-which in any way cause signicantinteraction between the concentric shafts.

While only a single embodiment of the invention has been fullydescribed, the details thereof are not to be construed as limitative ofthe invention. The invention contemplates such variations andmodifications as come within the scope of the appended claims.

We claim:

1. In plural shaft mechanism for radio receivers and the like, whereinan inner shaft is journalled in an outer shaft for adjusting inherentlylow-torque mechanism, such as a tuner, by one of said shafts: a systemfor preventing inadvertent turning of said shaft, comprising brake meansand brake shoe means normally bearing against said brake means, one ofsaid means being mounted on said shaft and rotatable therewith and theother being stationary with respect thereto.

Z. Apparatus as described in claim I wherein said brake means is a drummounted on said shaft, and said brake shoe means comprises stationaryclip means bearing against a peripheral surface of said drum` 3.Apparatus as described in claim 1, wherein said brake shoe meanscomprises a plurality of brake shoes.

4. Apparatus as described in claim 1 wherein said brake shoe meanscomprises a plurality of brake shoes symmetrically distributed withrespect to said brake means,

5. Apparatus as described in claim 4 wherein said brake means has adrum-shaped peripheral surface and sai-d brake shoes ybear radiallyagainst said peripheral surface.

6. Apparatus as described in claim 1, additionally including means forpreventing axial motion of one of said shafts relative to the other.

7. Control mechanism for a radio receiver, comprising a tuner; inner andouter shafts, one of said shafts being arranged for setting said tuner,the other shaft having means mounted thereon for controlling the volumeof the sound output of the receiver and said inner shaft beingjournalled in the outer shaft; and as means for preventing inadvertentturning of said one shaft, a brake drurn rotatable with said shaft, andstationary brake shoe means permanently bearing against said drum, saidshafts, brake drum, brake shoe means and means for controlling volumebeing in nested concentric relation.

3. Apparatus as described in claim 7 wherein said brake shoe meanscomprises stationary clips bearing against a peripheral surface of saiddrum.

References Cited UNITED STATES PATENTS 2,660,904 12/1953 Hilsinger74-531 X 3,053,110 9/1962 Shalek 74-531 FOREIGN PATENTS 962,098 6/ 1964Great Britain.

MILTON KAUFMAN, Primary Examiner.

7. CONTROL MECHANISM FOR A RADIO RECEIVER, COMPRISING A TURNER; INNER AND OUTER SHAFTS, ONE OF SAID SHAFTS BEING ARRANGED FOR SETTING SAID TURNER, THE OTHER SHAFT HAVING MEANS MOUNTED THEREON FOR CONTROLLING THE VOLUME OF THE SOUND OUTPUT OF THE RECEIVER AND SAID INNER SHAFT BEING JOURNALLED IN THE OUTER SHAFT; AND AS MEANS FOR PREVENTING 